Haven't had a huge amount of time for building lately, but have managed to machine a small 39mm I/D bayonet ring for the hull. This was turned from billet stock, and is machined to accept a small 1.5mm thick o-ring to minimise the room required for the seal and maximise access.

Easy job on a lathe pretty much hopeless if you haven't. Aluminium is chosen as it's easy to maintain tight tolerance, and also retains reasonable rigidity on a small thickness, which you just wouldn't achieve with plastic.

The ring is shown dry fitted to the hull, and will be bonded in with epoxy once a few other parts are installed.

There are no locking tabs, it's just a standard push fit like an end cap on a WTC.

You only need a latching mechanism when the hull is pressurized e.g. like some ballast systems do. As this boat is a dynamic diver with no internal pressure the friction of the o-ring is sufficient to keep the two halves together.

Adding integral tabs would also complicate machining quite a bit, but it's doable. You could index the tabs on a small lathe or if you're lucky to have one, a milling machine with a rotary table or dividing head. Various everyday items can be pressed into service for indexing e.g. the flats of a hexagonal nut. It's a little like making a crude gear.

As regards the rest of the machining operations, it's very similar to the machining of the plastic end caps which I detailed on the Youtube vids in the how-to section. The only real difference was that these are hollowed out, and I turned them from some aluminium bar stock rather than sheet plastic material. Also I machined my 'tube' rather than size the cap to fit pre-moulded tubing.

There is a little 'spinner' that goes on the nose of the craft, which allows the option of fitting small nut and screw to latch the two halves together, should it be required.

Brushless power brings the benefit of an efficient drive train, so there shouldn't be much heat produced. Also any heating of the air inside should be partly offset by the cooling effect of the water enveloping the hull.

Going by past experience, it's not uncommon to find you have a vacuum inside the hull especially if the air temperature is warm.

My Delphins are held together by screwing the nose cap on that has an O ring behind it.This pulls the nose section up against the tail section which has a larger O ring.Sandwiching the ring between the two sections. It tryed the screw on system like old German kit had but found it leaked a lot.At least my version did. BD.

Left the epoxy to fully cure through, and have plonked it in the test tank (bathroom sink) for a leak test, and it's tighter than a Scot on Burns night. Interestingly displacement came out at about 200 grams (7 ounces), about 11% more than calculated (based on the original vessels quoted 2.5 tonne displacement), so not too far out, and always handy when you have a bit more than expected.

Streamlining canopy moulded. This is one layer of 80g cloth and two layers of 110g cloth. Thin and light but with epoxy resin, bullet proof. Cloth moved slightly from the mould right at the front. I'll fix that in the mix by dobbing on a bit of thickened epoxy and putting it back in the tool to set. I've pencilled in the cut marks.

I don't consider my work 'amazing'. I endeavour to work to a good standard, in the case of this little thing I built it for two main reasons, firstly I've always liked the design, it looks very neat, and drives well (comparing against larger examples) and secondly I wanted to cut my teeth with moulding in epoxy laminates.

I've worked a fair bit with polyester, but only touched on epoxy. As with anything new, I prefer to start with something small, which limits the risk of failure. As such I made quite a few mistakes with this model, which I've managed to rectify, and those errors have been logged in mark one memory bank and will be avoided on the next project.